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{{pp-move-indef}}{{Standard model of particle physics}}In the physical sciences, subatomic particles are particles much smaller than atoms.WEB, Subatomic particles,weblink NTD, 5 June 2012, The two types of subatomic particles are: elementary particles, which according to current theories are not made of other particles; and composite particles.BOOK, Bolonkin, Alexander, Universe, Human Immortality and Future Human Evaluation, 2011, Elsevier, 9780124158016, 25, Particle physics and nuclear physics study these particles and how they interact.BOOK

, The idea of a particle underwent serious rethinking when experiments showed that light could behave like a stream of particles (called photons) as well as exhibiting wave-like properties. This led to the new concept of waveâparticle duality to reflect that quantum-scale "particles" behave like both particles and waves (they are sometimes described as wavicles to reflect this). Another new concept, the uncertainty principle, states that some of their properties taken together, such as their simultaneous position and momentum, cannot be measured exactly.{{Citation |first=W. |last=Heisenberg |title=Ãber den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik |language=de|journal=Zeitschrift fÃ¼r Physik |volume=43 |issue=3â4 |date=1927 |pages=172â198 |doi=10.1007/BF01397280 |postscript=. |bibcode = 1927ZPhy...43..172H }} In more recent times, waveâparticle duality has been shown to apply not only to photons but to increasingly massive particles as well.JOURNAL

, This has been verified not only for elementary particles but also for compound particles like atoms and even molecules. In fact, according to traditional formulations of non-relativistic quantum mechanics, waveâparticle duality applies to all objects, even macroscopic ones; although the wave properties of macroscopic objects cannot be detected due to their small wavelengths.BOOK

, Eisberg, R., Resnick, R., yes, 1985, Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles, John Wiley & Sons, 2nd, 59â60, 978-0-471-87373-0, For both large and small wavelengths, both matter and radiation have both particle and wave aspects. [...] But the wave aspects of their motion become more difficult to observe as their wavelengths become shorter. [...] For ordinary macroscopic particles the mass is so large that the momentum is always sufficiently large to make the de Broglie wavelength small enough to be beyond the range of experimental detection, and classical mechanics reigns supreme.

Dividing an atom

The negatively charged electron has a mass equal to {{frac|1837 or 1836}} of that of a hydrogen atom. The remainder of the hydrogen atom's mass comes from the positively charged proton. The atomic number of an element is the number of protons in its nucleus. Neutrons are neutral particles having a mass slightly greater than that of the proton. Different isotopes of the same element contain the same number of protons but differing numbers of neutrons. The mass number of an isotope is the total number of nucleons (neutrons and protons collectively).Chemistry concerns itself with how electron sharing binds atoms into structures such as crystals and molecules. Nuclear physics deals with how protons and neutrons arrange themselves in nuclei. The study of subatomic particles, atoms and molecules, and their structure and interactions, requires quantum mechanics. Analyzing processes that change the numbers and types of particles requires quantum field theory. The study of subatomic particles per se is called particle physics. The term high-energy physics is nearly synonymous to "particle physics" since creation of particles requires high energies: it occurs only as a result of cosmic rays, or in particle accelerators. Particle phenomenology systematizes the knowledge about subatomic particles obtained from these experiments.Taiebyzadeh, Payam (2017). String Theory; A unified theory and inner dimension of elementary particles (BazDahm). Riverside, Iran: Shamloo Publications Center. {{ISBN|978-600-116-684-6}}.

History

The term "subatomic particle" is largely a retronym of the 1960s, used to distinguish a large number of baryons and mesons (which comprise hadrons) from particles that are now thought to be truly elementary. Before that hadrons were usually classified as "elementary" because their composition was unknown.A list of important discoveries follows:{| class="wikitable"

Coughlan, G.D., J.E. Dodd, and B.M. Gripaios (2006). The Ideas of Particle Physics: An Introduction for Scientists, 3rd ed. Cambridge Univ. Press. An undergraduate text for those not majoring in physics.